Actuators

ABSTRACT

A rotary actuator has a piston comprising a vane-like member made up of a pair of opposed portions of similar form to each other and between which a pivot shaft of the piston is secured. Respective sealing rings extend peripherally around each of said opposed portions to provide a double line of sealing around the piston. Said portions are so shaped that they can be formed in a casting or moulding operation with mounting means for the sealing rings and engagement means for the shaft embodied in them, without the use of core pieces or like additional moulding members.

United States Patent 1191 1111 3,890,885 Nash June 24, 1975 [54] ACTUATORS 2,994,446 8/1961 Auwelaer et al 92 125 3,103,281 9/1963 Rumsey et a1. [76] Inventor: Alan Richard Brine Nash, 39 3 359 870 12 1967 P u H 92 125 Abbot/[,5 Ride a ng and urce .1

[22] Filed; J ly 13, 1973 Primary ExaminerPaul E. Maslousky [30] Foreign Application Priority Data July 21, 1972 United Kingdom 34366/72 [52] U.S. Cl. 92/125 [51] Int. Cl. F01c 9/00 [58] Field of Search 92/125, 124, 123, 122, 92/121, 120, 67; 91/339 [56] References Cited UNITED STATES PATENTS 2,951,470 9/1960 Self 92/125 2,975,763 3/1961 Grace 92/125 Attorney, Agent, or FirmNicho1 M. Sandoe ABSTRACT A rotary actuator has a piston comprising a vane-like member made up of a pair of opposed portions of similar form to each other and between which a pivot shaft of the piston is secured. Respective sealing rings extend peripherally around each of said opposed portions to provide a double line of sealing around the piston. Said portions are so shaped that they can be formed in a casting or moulding operation with mounting means for the sealing rings and engagement means for the shaft embodied in them, without the use of core pieces or like additional moulding members".

11 Claims, 12 Drawing Figures PATENTEB JUN 24 ms s3 9 0 8 8 5 SHEET v s ACTUATORS BACKGROUND OF THE INVENTION This invention relates to pressure-fluid operated actuators or motors, particularly actuators or motors of the kind in which a piston is mounted for rotary movement within a casing providing at least one chamber for the pressure fluid to act on the piston to displace the piston in an oscillatory manner through an angle of less than 360. Such motors or actuators will be referred to hereinafter simply as rotary actuators.

The operation of such actuators relies upon effective sealing by the piston of the two regions of the chamber on opposite sides of the piston. This, and the provision of means for mounting the piston to allow it to rotate in the casing leads to complex piston constructions that are expensive and difficult to produce.

SUMMARY OF THE INVENTION According to the present invention, a rotary actuator is provided with a piston comprising a substantially planar vane-like member, said piston being assembled from a plurality of parts comprising opposed portions forming said vane-like member, a plane of jointing of each of said opposed portions being substantially coincident with or parallel to a main central plane of the member. Conveniently, said portions of the member are of corresponding shape and abut each other directly, or with the interposition of no more than a very thin element, their plane of jointing being at a main central plane of the piston extending radially from its axis of rotation.

With such an arrangement, each said portion of the piston can advantageously have mounting means at or adjacent the plane of jointing for a peripheral sealing means of the piston that is provided to form a fluidtight seal between the piston and the chamber walls so as to prevent leakage of fluid past the piston. Said sealing means, in one preferred arrangement, comprise respective juxtaposed sealing rings, one engaged by each said portion of the vane-like member, and such a pair of sealing rings can be clamped together by said portions.

By virtue of the division of the vane-like member into opposed portions, it is possible to form the piston shaft as a separate member clamped between said portions. The shaft can be provided with splines, corrugations or other keying elements engageable with co-acting elements on said portions when the shaft is located between the portions, to prevent relative rotation therebetween. Where sealing means in the form of a pair of juxtaposed sealing rings is provided, said rings may extend along radially opposite sides of the shaft periphery to form a continuous line of sealing around the piston.

Advantageously, each of said opposed piston portions is a casting or moulding incorporating the sealing ring mounting means and/or the shaft-keying coating elements in such a manner that said means and/or elements are formed without the use of moulding cores.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. I is a schematic plan view of a rotary actuator, with the casing cover omitted, incorporating a piston according to the invention,

FIGS. 2 and 3 are side and sectional views of the piston, respectively,

FIG. 4 is an axial end view of one of the two cast or moulded portions of the piston vane,

FIGS. 5 to 7 are illustrations to different scales showing the lip sealing arrangement for the piston of the preceding figures, FIG. 5 illustrating a complete half seal,

FIG. 8 illustrates in section a portion of a piston according to the invention having an alternative form of lip sealing arrangement,

FIGS. 9 and 10 are side views of alternative pistons according to the invention, and

FIGS. 11 to 12 show two further forms of shaft for a piston according to the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring more particularly to FIGS. 1 and 2 of the drawings, a rotary actuator comprising a casing 1 is illustrated with its cover removed to show inside the casing a piston 2 comprising a vane 3 non-rotatably mounted on a shaft 4 that is journalled in the casing by bearing portions 6 to give the shaft an angular stroke of up to some The piston divides the casing interior into two spaces or chambers 10a, 10b isolated from each other by a peripheral lip seal arrangement 12 on the piston. Thus, by admitting pressure fluid through porting 14a or 14b in either of the respective spaces 8a, 8b the piston is rotated on its shaft. Further details of the actuator casing need not be described here since it can be of an entirely conventional form, and in the following description attention will be directed to the structure of the piston and its possible modification.

Details of a preferred form of piston according to the invention are shown in FIGS. 3 and 4 from which it can be seen that the vane of the illustrated piston comprises two identical half-members 16, each formed by a metal die-casting or a plastics moulding, having their interface in the radial plane of symmetry of the piston and being secured together by bolts 18.

As may be more clearly seen from the illustration of a half-member in FIG. 4, the mould parting line for each casting or moulding can be coincident with shoulder 20 of a peripheral recess 22 receiving a flexible lipseal (to be described below) so that no machining is required to prepare the seal seating. Similarly, splines 24 in a semi-cylindrical region 26, provided to engage non-rotatably with similar splines on the shaft, are disposed only on the bottom or inner portion of said region 26 so that they have no undercutting as regards the mould part forming the region 26 and can be fully formed in the die-casting or moulding process without the use of core pieces and without further finishing being required subsequently.

The lip seal arrangement 12 for the piston of the pre ceding figures is illustrated in more detail in FIGS. 5 to 7. It comprises two half-seals 30, placed back to back, each extending uninterruptedly around the peripheral recess 22 of its associated half-member. Each half-seal projects proud of the piston. Optionally, over the planar regions of the recess 22, a metal back-up plate 32 may be clamped between the half-seals and the halfmembers 16 to support each seal against undue distortion. Of course, in the semi-cylindrical regions 26 if this supporting function is required it can be exercised by the piston shaft.

The halfseal section comprises a bead 42 that seats in a complementary channel 44 in the face of the associated shoulder 20 of its half-member 16 to hold the half-seals positively in position on the piston vane. The section further comprises a wing 36 that projects laterally from the root portion 34 obliquely away from the periphery of the piston and that is arranged to have an interference fit with the casing inside wall surface the position of which relative to the piston is shown by the broken line 38 in FIG. 7. The two half-seals thus provide a double line of sealing and, because of the exposure of the inner face 40 of each wing 36 to the actuator fluid, the pressure of that fluid will tend to reinforce the sealing action.

A similar effect can be obtained with other forms of seal, one example of which is shown in FIG. 8. The two half-seals 46 in this instance also provide a double line of sealing. The half-seals are separated by rims 48 on the half-members 16, which can then be die-cast or moulded with the plane of their interface 50 as the parting plane of the dies. The half-seals can be moulded in situ on the half-members or bonded to them to be secured permanently in place. Keying elements may of course be provided to assist in securing the half-seals.

The separate piston shaft can take a variety of forms, some examples of which are illustrated in FIGS. 9 to 12.

The pistons shown in FIGS. 9 and 10 have their shafts secured to them in slightly modified manners as compared with the assembly shown in FIGS. 2 and 3. In both instances, the diameter of a central splined portion 52a of the shaft is larger than that of the bearing portions 6a to the extent that the roots of the spline are radially spaced outwardly from said portions 6a. In FIG. 9, one of the securing bolts 18a between the piston half-members also passes through a diametrical bore in the shaft so directly pinning the shaft to the piston. In the piston of FIG. 10, bolts 18b between the piston halves pass through diametrically opposite regions of a peripheral groove 56 in the shaft interrupting the splines of the portion 52a so that the clamping pressure of the bolts is thereby applied more directly to the splined engagement between the piston halves and the shaft than is the case in the arrangement shown in FIGS. 2 and 3.

In FIG. 11 an arrangement similar to that in FIGS. 2 and 3 is shown with splines 52b formed within the diameter of circular section end bearing portions 6b. In FIG. 12 the splines 520 are formed projecting above the bearing portions 6c and with their inside diameter greater than the diameter of the bearing portions.

It will be appreciated that the examples of the invention described above are capable of modification in many ways within the scope of the invention. In particular, where juxtaposed half-seals bear directly on each other they can be replaced by a single sealing member having a cross-section that is a composite of the sections of the two half-seals. Also, bonding or moulding in position of a sealing member can be carried out even in those cases where the member is mechanically keyed to its support, as by the beads 42 shown in FIGS. 5 to 7 What I claim and desire to secure by Letters Patent l. A rotary actuator having a piston comprising a pair of similar opposed portions secured together to form a substantially planar vane-like member and peripheral sealing means extending around said member, a plane ofjointing between said opposed piston portions being substantially coincident with a main central plane of the piston, a tubular recess being formed between said piston portions at one region of the piston, a shaft comprising bearing portions for mounting the piston in a rotary member extending into said tubular recess, and splines being provided on the shaft and on said opposed piston portions for interengagement to prevent rotation between the shaft and the piston portions, the shaft splines being formed by radially outwardly facing surfaces and the piston portion splines being formed by radially inwardly facing portions complementary to the shaft spline surfaces in engagement therewith, the splines on the two piston portions being confined to peripheral regions of the tubular recess remote from the plane of jointing.

2. A piston according to claim 1 wherein said portions of the member are of corresponding shape and abut each other whereby their plane ofjointing is at the central plane of the piston.

3. A piston according to claim 1 wherein said sealing means comprise respective juxtaposed sealing rings, one engaged by each said portion of the vane-like member.

4. A piston according to claim 3 wherein said sealing rings are clamped together by said portions.

5. A piston according to claim 4 wherein keying means are provided to retain the sealing rings positively in position on their piston portions.

6. A piston according to claim 3 wherein the sealing rings are permanently secured onto their respective piston portions.

7. A piston according to claim 3 wherein each sealing ring has a cross-section comprising a wing portion projecting obliquely away from the periphery of the piston and from the juxtaposed sealing ring whereby the sealing rings provide a double line of sealing around the piston.

8. A piston according to claim 3 wherein the piston portions are of cast or moulded form and mounting means for the sealing rings are embodied in said portions in the casting or moulding operation.

9. A rotary actuator piston comprising a pair of opposed rigid plane members secured together to form a substantially planar vane, a plane of jointing of each of said plate members being substantially coincident with a main central plane of the vane, a peripheral recess being provided on each of said plate members facing onto said plane of jointing, respective flexible sealing rings being engaged in said peripheral recesses, each sealing ring having a transverse cross-section comprising a first limb seating in the recess and a second limb projecting obliquely from said first limb peripherally outwardly and away from said plane of jointing to project peripherally outwardly of the piston plate members, a shaft being held between said plate members with the shaft axis substantially in said central plane, opposite ends of the shaft projecting from the vane and bearing portions being provided on said projecting ends for mounting the piston in a rotary manner, a series of axially directed splines being provided on the shaft between said projecting ends and a formation of splines being provided on respective opposed regions of the plate members for engagement with a plurality of the shaft splines on diametrically opposite portions of the shaft to secure the vane non-rotatably to the shaft, said formation of splines on each plate member being confined to a region spaced from the plane of jointing of the member, the individual splines of said formation having radially outwardly convergent faces and said faces being disposed at angles not more than 90 to the plane of jointing.

10. A piston according to claim 3 wherein the respective sealing rings disposed peripherally of the piston portions extend along radially opposite sides of the shaft periphery for each to form a continuous line of sealing around the piston periphery.

11. A rotary actuator having a piston comprising a pair of similar opposed portions secured together to form a substantially planar vane-like member, the joint between said opposed portions being substantially coincident with a main central plane of the piston, a tubular recess being formed between said portions, the axis of said recess lying in said central plane and being laterally offset towards one side edge of the planar member, a shaft comprising bearing portions for mounting the piston in a rotary manner being held in said recess between said opposed portions to project from opposite ends thereof, and peripheral sealing means extending around said vane-like member and the shaft projections form to said shaft splines, said recess splines being confined to portions of the recess surface remote from said central plane. 

1. A rotary actuator having a piston comprising a pair of similar opposed portions secured together to form a substantially planar vane-like member and peripheral sealing means extending around said member, a plane of jointing between said opposed piston portions being substantially coincident with a main central plane of the piston, a tubular recess being formed between said piston portions at one region of the piston, a shaft comprising bearing portions for mounting the piston in a rotary member extending into said tubular recess, and splines being provided on the shaft and on said opposed piston portions for interengagement to prevent rotation between the shaft and the piston portions, the shaft splines being formed by radially outwardly facing surfaces and the piston portion splines being formed by radially inwardly facing portions complementary to the shaft spline surfaces in engagement therewith, the splines on the two piston portions being confined to peripheral regions of the tubular recess remote from the plane of jointing.
 2. A piston according to claim 1 wherein saiD portions of the member are of corresponding shape and abut each other whereby their plane of jointing is at the central plane of the piston.
 3. A piston according to claim 1 wherein said sealing means comprise respective juxtaposed sealing rings, one engaged by each said portion of the vane-like member.
 4. A piston according to claim 3 wherein said sealing rings are clamped together by said portions.
 5. A piston according to claim 4 wherein keying means are provided to retain the sealing rings positively in position on their piston portions.
 6. A piston according to claim 3 wherein the sealing rings are permanently secured onto their respective piston portions.
 7. A piston according to claim 3 wherein each sealing ring has a cross-section comprising a wing portion projecting obliquely away from the periphery of the piston and from the juxtaposed sealing ring whereby the sealing rings provide a double line of sealing around the piston.
 8. A piston according to claim 3 wherein the piston portions are of cast or moulded form and mounting means for the sealing rings are embodied in said portions in the casting or moulding operation.
 9. A rotary actuator piston comprising a pair of opposed rigid plane members secured together to form a substantially planar vane, a plane of jointing of each of said plate members being substantially coincident with a main central plane of the vane, a peripheral recess being provided on each of said plate members facing onto said plane of jointing, respective flexible sealing rings being engaged in said peripheral recesses, each sealing ring having a transverse cross-section comprising a first limb seating in the recess and a second limb projecting obliquely from said first limb peripherally outwardly and away from said plane of jointing to project peripherally outwardly of the piston plate members, a shaft being held between said plate members with the shaft axis substantially in said central plane, opposite ends of the shaft projecting from the vane and bearing portions being provided on said projecting ends for mounting the piston in a rotary manner, a series of axially directed splines being provided on the shaft between said projecting ends and a formation of splines being provided on respective opposed regions of the plate members for engagement with a plurality of the shaft splines on diametrically opposite portions of the shaft to secure the vane non-rotatably to the shaft, said formation of splines on each plate member being confined to a region spaced from the plane of jointing of the member, the individual splines of said formation having radially outwardly convergent faces and said faces being disposed at angles not more than 90* to the plane of jointing.
 10. A piston according to claim 3 wherein the respective sealing rings disposed peripherally of the piston portions extend along radially opposite sides of the shaft periphery for each to form a continuous line of sealing around the piston periphery.
 11. A rotary actuator having a piston comprising a pair of similar opposed portions secured together to form a substantially planar vane-like member, the joint between said opposed portions being substantially co-incident with a main central plane of the piston, a tubular recess being formed between said portions, the axis of said recess lying in said central plane and being laterally offset towards one side edge of the planar member, a shaft comprising bearing portions for mounting the piston in a rotary manner being held in said recess between said opposed portions to project from opposite ends thereof, and peripheral sealing means extending around said vane-like member and the shaft projections at opposite ends of the recess, a series of axially directed and radially outwardly tapered splines being provided on the portion of the shaft in the recess, respective diametrically opposite portions of the recess being provided with series of splines of complementary form to said shaft splines, said recess splines being confined to portions of the recess surface remote from said central plane. 